Viral hemorrhagic fever: A syndrome caused by infection with one of a number of viruses that can cause increased permeability of the blood vessels resulting in bleeding into the skin, internally, or from the mouth or other orifices. The bleeding is usually not life-threatening. Other signs and symptoms of viral hemorrhagic fever (VHF) may also include high fever, weakness, dizziness, and myalgia. In severe cases, there may be shock, coma, delirium, seizures , and death.
The viruses that cause VHF belong to four families: the arenaviruses, filoviruses, bunyaviruses, and flaviviruses. The arenaviruses include the Lassa fever virus and Machupo, Junin, Guanarito, and Sabia hemorrhagic fever viruses. Among the filoviruses are the notorious Ebola virus and Marburg virus. The bunyaviruses include Rift Valley fever (RVF), Crimean-Congo hemorrhagic fever (CCHF), and hantaviruses. The viruses of yellow fever and dengue are Among the flaviviruses.
These are all RNA viruses that are covered, or enveloped, in a fatty (lipid) coating. The ability of these viruses to survive depends on an animal or insect host. These viruses are geographically restricted to the areas where their host species live. Humans are infected when they come into contact with infected hosts. However, with some of these viruses, after the transmission from the natural host, there can be person-to-person transmission. Human cases or outbreaks of hemorrhagic fevers caused by these viruses occur sporadically and irregularly. The occurrence of outbreaks cannot be easily predicted.
With a few exceptions, there is no established drug treatment for VHFs. Ribavirin, an anti-viral drug, has been effective in treating some patients with Lassa fever. Treatment for most of the VHFs is largely supportive.